The goal of this clinical trial is to evaluate whether immersive virtual reality (VR)-based physiotherapy is effective in improving balance, reducing fall risk, and enhancing cardiorespiratory exercise capacity in individuals with Parkinson's disease. The main questions it aims to answer are:

Does immersive VR therapy improve postural balance more effectively than conventional physiotherapy?

Does immersive VR reduce fall risk and increase cardiorespiratory fitness compared with standard physiotherapy?

Researchers will compare an immersive VR intervention with conventional physiotherapy to determine whether VR can produce superior functional and physiological outcomes in patients with Parkinson's disease.

Participants will:

Be randomly assigned (1:1) to an experimental group (immersive VR therapy) or a control group (conventional physiotherapy).

Take part in structured physiotherapy sessions focused on balance, mobility, and functional capacity.

Undergo pre- and post-intervention assessments of balance, fall risk, cardiorespiratory exercise capacity, and quality of life.

This randomized controlled trial (RCT) with parallel assignment will include 50 participants (25 per group). Randomization will be performed using the OxMaR (Oxford Minimization and Randomization) software, which enables adaptive randomization to ensure balanced baseline characteristics between groups.

Secondary objectives include evaluating the impact of immersive VR on health-related quality of life and comparing treatment adherence between VR-based and conventional physiotherapy interventions.

Neurological disorders are among the leading causes of disability worldwide, significantly affecting functional independence, mobility, and quality of life. Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by dopaminergic neuron loss in the substantia nigra, resulting in motor and non-motor symptoms that compromise multiple physiological systems. The main motor symptoms-bradykinesia, rigidity, resting tremor, and postural instability-directly impair balance and substantially increase the risk of falls. Additionally, individuals with PD often exhibit reduced cardiorespiratory fitness, which contributes to functional decline, decreased participation in daily activities, and increased caregiver burden.

Physiotherapy plays a crucial role in the comprehensive management of PD, targeting improvements in balance, mobility, motor function, and cardiorespiratory capacity to delay disability and promote autonomy. In recent years, emerging technologies have transformed conventional rehabilitation paradigms, with virtual reality (VR) gaining recognition as a promising tool for enhancing therapeutic outcomes.

Immersive VR systems provide controlled, interactive, and multisensory environments that facilitate repetitive, task-oriented motor practice with immediate sensory feedback. These features can increase motivation, engagement, and adherence to therapy, while simultaneously stimulating both motor and cognitive domains. Moreover, VR interventions may induce neuromodulation processes by activating and reorganizing neural circuits, thereby promoting neuroplasticity - a fundamental mechanism for functional recovery in neurodegenerative diseases such as PD.

Preliminary research suggests that VR-based rehabilitation can lead to measurable improvements in balance, reduction in fall risk, and enhancement of physical endurance. However, the current body of evidence remains limited by small sample sizes, heterogeneous methodologies, and a lack of direct comparisons with conventional physiotherapy. Gaps persist regarding which subgroups of PD patients benefit most, the medium- and long-term effects of VR interventions, and the neurophysiological mechanisms underlying these improvements.

This randomized controlled trial (RCT) aims to address these limitations by conducting a rigorous evaluation of an immersive VR intervention compared to standard physiotherapy in individuals with PD. A total of 50 participants will be randomly assigned (1:1) to either a VR group or a conventional physiotherapy group using the OxMaR (Oxford Minimization and Randomization) software, which employs adaptive minimization to balance baseline characteristics between groups.

The primary objective is to determine whether immersive VR therapy leads to greater improvements in postural balance, fall risk reduction, and cardiorespiratory exercise capacity compared to conventional physiotherapy. Secondary objectives include assessing changes in health-related quality of life and evaluating adherence to treatment protocols across intervention groups.

By integrating neurorehabilitation principles with immersive technology, this study aims to contribute robust scientific evidence supporting the use of VR as an effective physiotherapeutic tool for enhancing functional outcomes and overall well-being in individuals with Parkinson's disease.

Inclusion Criteria:

• Age between 55 and 75 years.
• Clinical diagnosis of Parkinson's disease confirmed by a neurologist.
• Mild to moderate disease stage (Hoehn and Yahr I-III).
• Ability to understand and follow simple instructions and actively participate in the intervention.
• Signed informed consent provided before participation.

Exclusion Criteria:

• Severe cognitive impairment, defined as a Montreal Cognitive Assessment (MoCA) score < 21.
• Severe musculoskeletal comorbidities that limit mobility or prevent participation in physiotherapy sessions.
• Visual or vestibular disorders that would compromise safe use of virtual reality equipment.
• Serious medical complications during the study (e.g., acute cardiovascular events such as myocardial infarction or stroke) that may endanger the participant or interfere with treatment.
• Adverse effects related to the intervention, including severe dizziness, persistent nausea, disorientation, or headaches that prevent continuation of therapy.
• Lack of adherence to the protocol, defined as missing four or more intervention sessions without justification.
• Significant worsening of neurological status or new complications that contraindicate participation in physiotherapy.
• Surgical or medical procedures unrelated to Parkinson's disease that affect general mobility or the ability to participate in the intervention.